From an international perspective there are two established ways to address this request. In the gTLD space zone files are public. Every registrar can download them and access them. This opens the door to many ways of abuse as we see it since many years (DROA comes to mind (http://bit.ly/7aAOr) as well as spam in general) but on the other side satisfies the needs of interested parties to get the data they want. in reality it is not that easy as there are many privacy services that do proxy registration so that the actual owner is only known to the registrar and not even to the registry. This practice is common use in TLDs that publish their zone files and actually make it harder to get information in case it is really needed.
The other approach is to restrict access to the information published on whois. This is what most ccTLD registries do and that has a good reason. Abuse of domain related information is way below the levels of comparable gTLD zones. The effect is also that the practice of proxy registration is not common as there is no need to. This ensures a higher quality of data on a registry level and hence a better way of getting actual information (eg for RDS or other legal inquiries).
Everyone requesting more extensive search capabilities across registrant information should first look at the risks before suggesting solutions. This is a dangerous game and especially the less technical focused should be highly advised to request some informed input before judging on a solution in this case.